Author's solution: O(N^4)

GPT's solution: O(N)

:skull:

Author's solution: O(N^4)

GPT's solution: O(N)

:skull:

Another year, another IOI

not much comments to be made here

Official website: https://ioi2026.uz/

Schedule: https://ioi2026.uz/schedule

Scoreboard: https://ranking.ioi2026.uz/

Participants: https://codeforces.me/blog/entry/153182

Day 1: 09:00 — 14:00 GMT+5, August 11th, 2026

Day 1 official problemset: https://github.com/ioi/task-archive/tree/master/2026/day1

First ACs:

P1: I_love_Khanh_Dan at 04:13

P2: Z-301 at 02:19

P3: Kevin114514 at 00:19

Day 2: 09:00 — 14:00 GMT+5, August 13th, 2026

Day 1 official problemset: https://github.com/ioi/task-archive/tree/master/2026/day2

First ACs:

P4: None

P5: at 02: 21

P6: Kevin114514 at 02:39

==================================================

Additional contents:

gsPVH's Day1 commentary: https://www.youtube.com/watch?v=H3dQF7JdoIM

gsPVH's Day2 commentary: https://www.youtube.com/watch?v=WDQRR17RsKg

(both streams starts 30 min before the respective competition day)

Other discussion blog: https://codeforces.me/blog/entry/155911

Another year, another TST.

Now that I'm in university, I can "accidentally" "forget" to go to school, so expect scoreboard streams from the very beginning this time around. Still autistic as ever.

Top 32 in Vietnamese Olympiad in Informatics 2026 + APIO25 contestants who are still eligible for this year will compete in 2 competition days. Top 15 progresses to APIO.

IOI26 selection score = TST26 Day1 score + TST26 Day2 score + APIO26 score. Top 4 contestants will be Vietnam's representatives for IOI26 should things not go wrong

List of participants: https://docs.google.com/spreadsheets/d/1l0dEH-Viujw4NpRuyn9HF4KVxgJ-jDi5HKV60UFJLc8/edit?gid=594021204#gid=594021204

Full problemset (based on contestant's recollections, no submit): here

Contest schedule:

Day 0 (Equipment testing): 25/03/2026

Day 1 (Competition Day 1): 26/03/2026 (08:00 GMT+7 — 13:00 GMT+7)

Day 2 (Competition Day 2): 27/03/2026 (08:00 GMT+7 — 13:00 GMT+7)

Note cho những người muốn đến hóng scoreboard trực tiếp: Khác với các năm trước (ít nhất từ 2017), do UET đã hoàn thành công cuộc cải tổ gì đấy nên địa điểm thi (và xem live scoreboard) không còn ở G2 VNU nữa. Địa điểm thi đã được chuyển sang tòa E2 của VNU (hình ảnh ở đây). Scoreboard sẽ được chiếu ở phòng 212 E2

Links:

Discussion thread on VNOI Discord: https://discord.com/channels/660930260405190688/1006418260637528065/threads/1485570568357941339

Day 1 scoreboard:

Day 1 Livestream + Commentary: here

Day 1 Livestream + Commentary (gsPVH version): here

Day 1 Problemset (Contestant's recollections): here

You can upsolve the Day1 problems here: [To be added in 2027, soonTM]

Day 2 scoreboard:

Day 2 Livestream + Commentary: here

Day 2 Livestream + Commentary (gsPVH version): here

Day 2 problemset (contestants' recollections, unofficial tests): See above

Greetings.

Another year, and another IOI is quickly approaching. The residential IOI maniac has returned, this time with non-zero contribution to the IOI community in one way or another.

Discuss about things here. Problem solutions. Funny things. Feedbacks that the organizing committees would really be dying to know about.

Good luck, and have fun!

(Aside from the live scoreboard and problem links, so "big stuffs", other tidbits of information will be in the comments. The thread from last year looked like a mess)

You can find the daily schedule here. Note that the local timezone is GMT-4

According to the schedule, the date of the competition days will be:

Practice Session: 10:00 — 12:00 July 28

Competition Day 1: 10:00 — 15:00 July 30

Competition Day 2: 10:00 — 15:00 August 1

Live scoreboard can be found here. Note that it is currently displaying the practice session results for the time being (Scoreboard should be up by now)

The tasks (alongside with some really good writeups) can be found here

For the next 2 days (March 26-27, 2025), Vietnamese TST will take place. Top 15 contestants will advance to APIO. Amongst top 15, top 4 when ranked by TST+APIO score will make it to the IOI.

List of contestants: https://docs.google.com/spreadsheets/d/1s_8uAJwc9H5XJI6W7PMqPJDo269NBHlzbaiROKC5VXs/edit?gid=594021204#gid=594021204

I will be present at the scoreboard room to wait for the results (and preferably enter full autistic fanboy mode) at around 01:00 of the day1 contest and 02:45 for Day2. Expect a livestream of the scoreboard room. Problems will probably be "leaked" here eventually.

Link for day 1 stream (the webcam is utter dogshit): https://www.youtube.com/live/iB-T85xUxOM?si=xWGQ0CsSqbjzjFLt

Link for day 2 stream: https://www.youtube.com/live/KVV_dbfd-Js?si=KbvF0A38RvVS4te6

New link with 100x the quality (because wifi sucks): https://youtube.com/live/jMcjeueVIs4?feature=share

[2026 Update]: You can now upsolve the tasks with unofficial testcases:

Day 1: https://oj.vnoi.info/contest/tst25_day1

Day 2: https://oj.vnoi.info/contest/tst25_day2

Local terminal IOI addict/enthusiast here.

Last year, a grand total of 0 discussion blogs for the IOI appeared, and around 0 discussions on the tasks were made (despite possibly the most (comparatively) interesting problemset since....2016/2018 or something). For this year, I'd like to take matters into my own hands and open this blog.

Dump things here. Predictions. Links for live scoreboards. Writeup for tasks the way it have been for 20217/2019/2021 or something. Problemsetters coming out (not like that, I mean, the way Pajaraja did in 2021 (for Fountain Parks) or E869120 (for Prisoner Challenge)......or the at least 15 times people have done that. Still think that the lack of discussion of IOI2023 tasks was really sad — actually had to resort to shitty translated Luogu blogs for that.

Contest Schedule & Important Links:

(Time in GMT+3 (Egypt local time), convert that to your local timezone, dummy!)

(A more comprehensive schedule can be found here: https://www.ioi2024.eg/schedule)

- Contest Day 1: 09:00 — 14:00 03/09/2024 (Sept.3, 2024)

- Contest Day 2: 09:00 — 14:00 05/09/2024 (Sept.5, 2024)

- Awards & Closing Ceremony: 19:00 — 21:00 06/09/2024 (Sept.6, 2024)

**Live Scoreboard: https://ranking.ioi2024.eg/ **

The thread from ko_osaga can be found here

You can submit your solutions here:

Day 1 tasks can be found here

Day 2 tasks can be found here

Official Results can be found here

Major update: 2 Chinese contestant got 50% of their points on Day2 taken away + 1 disqualified. Only Zhoukangyang remains.

https://stats.ioinformatics.org/results/2024

Highlight of the year:

Congratulations to hirayuu_cf for winning a Gold-1 in his first IOI.

A bunch of links starts here.

The live recording of the opening ceremony can be found here:

The live recording of the closing ceremony can be found here

The Twitter of the Japanese Delegate Vice President could be found here. You can (obviously) find the corresponding Japanese IOI contestants' Twitter there.

Here's the official Facebook account of the IOI. Follow that for some updates

Here's the album dedicated to Vietnam's IOI24 team.

(more to add in later on. Delegation leaders, chug the link of your country's photos and stuffs here so that I can add in later)

Here's the list of contestants & their corresponding teams. Best of luck.

Here's a recursive function.

Here's the prediction blog.

Here's where you can bet virtual money on the amount of medals European countries will won in IOI24. Practice your better mentality for the upcoming World Cup, starting from NOW!!!!

Here's the Swiss Olympiad in Informatics' blog on IOI24

Here's Errichto's live commentary/stream VOD

Here's Errichto's live commentary VOD for day 2.

Here's a spreadsheet with statistics of all recorded IOI problems.

Here's what to do after you AK the contest in 3 hours. Conggratulations to zhoukangyang for the win on day 1.

.......and day 2, I guess. Congratulations to zhoukangyang on the perfect win. You can rest now.

The list of links ends here